SilverStone Nightjar 500 W Power Supply Review

Primary Analysis

On this page we will take an in-depth look at the primary stage of the SilverStone Nightjar 500 W. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one GBJ1506 rectifying bridge, which is attached to the same heatsink as the primary transistors. This bridge supports up to 15 A at 100° C, so in theory, you would be able to pull up to 1,725 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning itself out. Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.

Figure 12: Rectifying bridge

The active PFC circuit uses two SPW20N60C3 MOSFETs, each supporting up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode (note the difference temperature makes), or 62.1 A at 25° C in pulse mode. These transistors present a 190 mΩ resistance when turned on, a characteristic called RDS(on). The lower the number is, the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

The output of the active PFC circuit is filtered by four 150 µF x 400 V Japanese electrolytic capacitors from Chemi-Con, labeled at 105° C. Since they are connected in parallel, they are the equivalent of a single 600 µF x 400 V capacitor. Splitting a single capacitor into several smaller ones was performed in order to improve thermal dissipation, which is one of the main concerns with fanless power supplies.

The active PFC circuit is controlled by an NCP1653A integrated circuit.

Figure 13: Active PFC controller

In the switching section, the SilverStone Nightjar 500 W uses a single-transistor forward configuration with an active clamp. An SPW17N80C3 MOSFET is used as the main switching transistor, while an FQPF3N80C is utilized for the active clamp part. The main transistor supports up to 17 A at 25° C or 11 A at 100° C in continuous mode, or 51 A at 25° C in pulse mode, with an RDS(on) of 290 mΩ, while the second transistor supports up to 3 A at 25° C or 1.9 A at 100° C in continuous mode, or 12 A at 25° C in pulse mode, with an RDS(on) of 4.8 Ω (4,800 mΩ).

In Figure 14, the manufacturer added a copper plate between the transistors and the heatsink to increase thermal dissipation.

Figure 14: The active PFC transistors, main switching transistor, and active clamp transistor

The switching transistors are controlled by an NCP1562B integrated circuit.

Figure 15: PWM controller

Let’s now take a look at the secondary of this power supply.